Arch Windows: Determin the Radius of the Molding

Installing Molding around an Arch Window

If the measurement from A to B is 60 inches, then the radius would be half of that, or 30 inches. This window would need an arch molding with an inside radius of at least 30 inches like the ER-8751-180. You can always go a little bigger on the arch radius and paint the exposed wall the same color as the molding with excellent results.

This will only work with a window that is a semi-circle. If you aren't sure if yours is a semi-circle, measure the distance between A and B of the window or doorway. Then measure from the top of the arch to the window (the C measurement). If the C measurement is different than half of the A to B measurement then your arch is not a semi-circle. For those windows or doorways you can read about how to create an Arch Molding.